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Atmosphere
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Brake Wear Particulate Matter and Mitigation Strategies
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Brake Wear Particulate Matter and Mitigation Strategies

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Aerosols".

Deadline for manuscript submissions: closed (28 February 2023) | Viewed by 19910

Special Issue Editors

Dr. Marcel Mathissen

E-Mail Website
Guest Editor
Ford-Werke GmbH, Süsterfeldstr, 200, 52072 Aachen, Germany
Interests: non-exhaust particle emissions; brake wear; tyre wear; resuspension
Dr. Theodoros Grigoratos

E-Mail Website
Guest Editor
Joint Research Centre (JRC), European Commission, Via E Fermi 2749, 21027 Ispra, Italy
Interests: non-exhaust particle emissions; brake wear; microplastic-tire emissions; air pollution; GHG emissions mitigation

Special Issue Information

Dear Colleagues,

Non-exhaust particle emissions (including tyre, road, and brake wear) are projected to be dominating particle emissions from road traffic at least when modern vehicle fleets are examined. Exhaust particle emission levels are regulated and were significantly reduced in the last decades. In contrast, non-exhaust emissions are expected to further increase due to the increase in traffic. In this context, the United Nations Economic Commission for Europe World Forum for Harmonization of Vehicle Regulations (UNECE WP.29) has decided to develop a Global Technical Regulation on brake emissions from light duty vehicles. At the same time, the EU plans to include brake wear particle emissions in the upcoming EURO 7 emission standards legislation.

This special issue is trying to summarize the current state-of-the-art in the field of brake wear particle emissions. This includes basic research of the tribological formation mechanisms, progress on standardization efforts for measuring Particle Mass (PM) and Particle Number (PN) emissions from different types of brakes in a repeatable and reproducible way, as well as the influence of brake wear mitigation measures. Here, a special focus is given on regenerative braking and its potential to reduce PM and/or PN emissions compared to fully conventional ICE vehicles. Finally, the influence of possible future technologies in reducing brake emissions will be examined.

Dr. Marcel Mathissen
Dr. Theodoros Grigoratos
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Atmosphere is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • aerosol
  • brake wear
  • non-exhaust
  • particle mass
  • particle number
  • regeneration
  • electric vehicles
  • emission factor

Published Papers (7 papers)

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Research

31 pages, 6503 KiB  
Article
Comprehensive Analysis of Current Primary Measures to Mitigate Brake Wear Particle Emissions from Light-Duty Vehicles
by Lukas Storch, Christopher Hamatschek, David Hesse, Felix Feist, Thomas Bachmann, Philipp Eichler and Theodoros Grigoratos
Atmosphere 2023, 14(4), 712; https://doi.org/10.3390/atmos14040712 - 14 Apr 2023
Cited by 10 | Viewed by 3633
Abstract
Exhaust regulations and improved exhaust gas treatment systems have already initiated the trend that brings emissions from brakes and tires to the forefront of traffic-induced particulate matter. The health and environmental relevance of particulate matter has resulted in regulators, industry, and research institutions [...] Read more.
Exhaust regulations and improved exhaust gas treatment systems have already initiated the trend that brings emissions from brakes and tires to the forefront of traffic-induced particulate matter. The health and environmental relevance of particulate matter has resulted in regulators, industry, and research institutions prioritising the mitigation of non-exhaust particle emissions. To this end, under the umbrella of the United Nations Economic Commission for Europe World Forum for Harmonisation of Vehicle Regulations (UNECE WP.29), the Working Party on Pollution and Energy (GRPE) mandated the Particle Measurement Programme Informal Working Group (PMP-IWG) to develop a Global Technical Regulation (GTR) for measuring brake dust. The standards and procedures defined within the GTR should eventually form the basis for the introduction of a Euro 7 limit value for brake emissions. The purpose of this measurement campaign is to provide an exemplary overview of the emission behaviour of wheel brakes and friction pairings currently available on the market and to identify possible reduction potential with regard to particulate emissions. All measurements were carried out taking into account the draft GTR valid at the time of execution. For the investigations, brakes were selected using the example of different vehicle classes, brake concepts (disc and drum brake), vehicle axles (front and rear axle), and alternative friction materials (brake disc and pads/shoes). Thus, the use of wear-resistant discs and improved brake pad compositions are able to achieve significantly lower emissions. In addition, the measurement of brake dust emissions from vehicles with different levels of electrification was considered. Electrical braking was modelled and applied to the Worldwide Harmonised Light-Duty Vehicles Test Procedure (WLTP) Brake Cycle, which has demonstrated high emission reduction potentials depending on the electrification level. Full article
(This article belongs to the Special Issue Brake Wear Particulate Matter and Mitigation Strategies)
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25 pages, 2781 KiB  
Article
Interlaboratory Study on Brake Particle Emissions—Part I: Particulate Matter Mass Emissions
by Theodoros Grigoratos, Marcel Mathissen, RaviTeja Vedula, Athanasios Mamakos, Carlos Agudelo, Sebastian Gramstat and Barouch Giechaskiel
Atmosphere 2023, 14(3), 498; https://doi.org/10.3390/atmos14030498 - 4 Mar 2023
Cited by 14 | Viewed by 2420
Abstract
The Particle Measurement Programme Informal Working Group (PMP-IWG) coordinated a global interlaboratory study (ILS) on brake wear particle emissions with the participation of 16 testing facilities. Two articles present the main outcomes of the ILS: (I) Particulate matter mass (PM), and (II) Particle [...] Read more.
The Particle Measurement Programme Informal Working Group (PMP-IWG) coordinated a global interlaboratory study (ILS) on brake wear particle emissions with the participation of 16 testing facilities. Two articles present the main outcomes of the ILS: (I) Particulate matter mass (PM), and (II) Particle Number (PN) emissions. The test matrix covered a wide variety of brake systems and configurations. The tested disc brakes were found to emit PM2.5 and PM10 that varied between 0.8–4.0 mg/km and 2.2–9.5 mg/km per brake, respectively, depending on the type of brake and the applied testing load. The drum brake emitted much lower PM due to its enclosed nature. Almost 37–45% of the emitted PM falls in the fine particle size with this fraction being higher for the drum brake. On the other hand, almost 50–65% of the total brake mass loss falls in particle sizes larger than 10 μm or gets lost before being measured. The most important loss mechanisms for PM in the proposed layout are being discussed. Finally, the PM measurement variability and lab-to-lab reproducibility are investigated. Full article
(This article belongs to the Special Issue Brake Wear Particulate Matter and Mitigation Strategies)
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18 pages, 6300 KiB  
Article
Airborne Brake Wear Emissions from a Battery Electric Vehicle
by Linda Bondorf, Lennart Köhler, Tobias Grein, Fabius Epple, Franz Philipps, Manfred Aigner and Tobias Schripp
Atmosphere 2023, 14(3), 488; https://doi.org/10.3390/atmos14030488 - 1 Mar 2023
Cited by 11 | Viewed by 3479
Abstract
Although traffic exhaust emissions in Europe have been drastically reduced, airborne particle emissions caused by brakes and tires are still increasing with the number of vehicles. The measurement of non-exhaust emissions is an emerging technological challenge. We present a custom measurement setup to [...] Read more.
Although traffic exhaust emissions in Europe have been drastically reduced, airborne particle emissions caused by brakes and tires are still increasing with the number of vehicles. The measurement of non-exhaust emissions is an emerging technological challenge. We present a custom measurement setup to investigate the brake- and tire-wear emissions of an in-use battery electric vehicle. A separate brake housing and HEPA ventilation enabled airborne brake wear emissions to be measured under realistic conditions without external influences. The emission tests on a chassis dynamometer included particle number concentrations and particle size distribution for diameters of 4 nm to 10 μm. Emission indices were determined for three driving cycles: WLTC Class 3b, WLTC Brake Part 10, and a real driving cycle. Further investigations focused on emission control through regenerative braking and brake coating. Driving with regenerative braking reduced emissions by up to 89.9%, which related to the concentration of particles in the ultrafine/fine size range. Hard-metal brake coating led to a further significant reduction in emissions of up to 78.9%. The results point the way to future RDE measurement of non-exhaust emissions and show the potential of regenerative braking and brake coating to reduce airborne brake wear emissions. Full article
(This article belongs to the Special Issue Brake Wear Particulate Matter and Mitigation Strategies)
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18 pages, 3963 KiB  
Article
Interlaboratory Study on Brake Particle Emissions Part II: Particle Number Emissions
by Marcel Mathissen, Theodoros Grigoratos, Sebastian Gramstat, Athanasios Mamakos, RaviTeja Vedula, Carlos Agudelo, Jaroslaw Grochowicz and Barouch Giechaskiel
Atmosphere 2023, 14(3), 424; https://doi.org/10.3390/atmos14030424 - 21 Feb 2023
Cited by 10 | Viewed by 2623
Abstract
The Particle Measurement Programme (PMP) informal working group co-ordinated a global interlaboratory study (ILS) on brake wear particle emissions with the participation of 16 laboratories in 2021. Two articles present the results of the ILS: (I) particulate matter mass (PM) and (II) particle [...] Read more.
The Particle Measurement Programme (PMP) informal working group co-ordinated a global interlaboratory study (ILS) on brake wear particle emissions with the participation of 16 laboratories in 2021. Two articles present the results of the ILS: (I) particulate matter mass (PM) and (II) particle number (PN) emissions. The test matrix covered different brake systems, including ECE and NAO pad materials with grey cast iron discs and a drum brake. Regarding PN, the study measured the total particle number from approximately 10 nm to 2.5 µm (TPN). Some testing facilities measured solid particle number emissions (SPN) in parallel. The mean TPN concentrations ranged from 9.1 × 108 #/km/brake to 1.1 × 1010 #/km/brake. TPN and SPN emission levels were comparable, except for one lab that measured very high volatile particle emissions for one brake system. The minimum and maximum SPN emissions for a given brake differed by a factor of 2.5 ± 0.5, comparable to data from exhaust SPN ILS measurements. This article provides an overview of lessons learned and subsequent measures incorporated in an upcoming global technical regulation to reduce measurement variability when sampling and measuring brake particle emissions for light-duty vehicles up to 3.5 t. Full article
(This article belongs to the Special Issue Brake Wear Particulate Matter and Mitigation Strategies)
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17 pages, 2020 KiB  
Article
Characterization of Particle Number Setups for Measuring Brake Particle Emissions and Comparison with Exhaust Setups
by Theodoros Grigoratos, Athanasios Mamakos, Michael Arndt, Dmytro Lugovyy, Robert Anderson, Christian Hafenmayer, Mikko Moisio, Joonas Vanhanen, Richard Frazee, Carlos Agudelo and Barouch Giechaskiel
Atmosphere 2023, 14(1), 103; https://doi.org/10.3390/atmos14010103 - 3 Jan 2023
Cited by 7 | Viewed by 1989
Abstract
The stringency of vehicle exhaust emissions regulations resulted in a significant decrease in exhaust particulate matter (PM) emissions over the years. Non-exhaust particles (i.e., from brakes and tyres) account for almost half or more of road transport-induced ambient PM. Even with the internal [...] Read more.
The stringency of vehicle exhaust emissions regulations resulted in a significant decrease in exhaust particulate matter (PM) emissions over the years. Non-exhaust particles (i.e., from brakes and tyres) account for almost half or more of road transport-induced ambient PM. Even with the internal combustion engine ban in 2035, electrified vehicles will still emit PM from brake and tyre wear. Consequently, non-exhaust PM emissions cannot decrease significantly without any regulatory measures. Because independent research carried out under different methods is not readily comparable, a Global Technical Regulation (GTR), which sets the procedures and boundaries of testing brake wear particle emissions, is currently under development. This overview describes the particle number (PN) measurement setup based on the well-known exhaust emissions PN methodology. We provide the technical requirements and the expected maximum losses. In addition, we estimate the effect of particle losses on the differences between different setups for typical size distributions observed during brake testing. Finally, we compare brake testing PN specifications to those of exhaust PN. Full article
(This article belongs to the Special Issue Brake Wear Particulate Matter and Mitigation Strategies)
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14 pages, 2287 KiB  
Article
Development of Dust Collectors to Reduce Brake Wear PM Emissions
by Sang-Hee Woo, Gunhee Lee, Bangwoo Han and Seokhwan Lee
Atmosphere 2022, 13(7), 1121; https://doi.org/10.3390/atmos13071121 - 15 Jul 2022
Cited by 2 | Viewed by 1777
Abstract
In this study, two different dust collectors, one based on an inertial separator and the other based on an electrostatic precipitator (ESP), were developed in order to reduce brake wear particulate matter (PM) emissions. Additionally, the collection efficiencies for brake wear particles (BWPs) [...] Read more.
In this study, two different dust collectors, one based on an inertial separator and the other based on an electrostatic precipitator (ESP), were developed in order to reduce brake wear particulate matter (PM) emissions. Additionally, the collection efficiencies for brake wear particles (BWPs) of the inertial separator and the ESP were evaluated according to brake pad type. In the case of the inertial separator, the BWP collection efficiencies for the low-metallic (LM) and non-asbestos organic (NAO) pads were similar, and the cut-off size at 50% collection efficiency (D50) was 2.2 µm. The ESP was designed without an additional electrostatic charging device because naturally induced electrostatic charging occurred due to the friction between the brake disc and pad. The BWP collection efficiency of the ESP was higher for NAO pad than for LM pad because the BWPs generated from the NAO pad contained a relatively low iron (Fe) component compared to that of the LM pad, thereby generating more frictional electricity. The maximum ESP collection efficiencies of the BWPs generated from the LM and NAO pads were determined to be 60% and 75%, respectively, and the remaining BWPs that were not collected were presumed to be particles that were not frictionally charged. Full article
(This article belongs to the Special Issue Brake Wear Particulate Matter and Mitigation Strategies)
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15 pages, 3915 KiB  
Article
Electron Microscopic Characterization of the Brake Assembly Components (Disc and Pads) from Passenger Vehicles
by Panayotis Dimopoulos Eggenschwiler, Daniel Schreiber, Viola Papetti, Sebastian Gramstat and Dmytro Lugovyy
Atmosphere 2022, 13(4), 523; https://doi.org/10.3390/atmos13040523 - 25 Mar 2022
Cited by 4 | Viewed by 2083
Abstract
The present work focuses on a detailed analysis of new and used braking friction partners (discs and pads) in order to provide a comprehensive characterization of the source of the airborne particles formed during braking. Scanning electron microscopy (SEM) combined with energy dispersive [...] Read more.
The present work focuses on a detailed analysis of new and used braking friction partners (discs and pads) in order to provide a comprehensive characterization of the source of the airborne particles formed during braking. Scanning electron microscopy (SEM) combined with energy dispersive X-Ray analysis (EDX) was applied to investigate the new brake disc and new and used brake pad components of a passenger vehicle. The pads include at least 21 different substances, involving carbonaceous particles, oxides, sulfides, sulfates and silicates of Al, Si, K, Ca, Ti, Fe, Zr, Sn, less Mg, Ba, Na and, rarely, Bi and Zn, as well as K-titanate. Aramid and phenolic resin are also present, enriched toward the metal interface. The size of the pad constituents extends over a very wide range, from hundreds of µm to a few µm, and goes down to hundreds of nm and, rarely, tens of nanometers. Carbonaceous particles with sizes down to a few tens of nanometers occupy ca. 16% of the total of the pad constituents. Abundant Zr-bearing phases, as well as various other phases involving S, Ca, Mg, Si, Ti and, to a lower extent, Ba and Fe in different combinations, constitute the pad main matrix. Full article
(This article belongs to the Special Issue Brake Wear Particulate Matter and Mitigation Strategies)
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